You could always go to Mehrunes Dagon's shrine and
I think you're better off finding such a weapon inside a dungeon's main treasure chest, if you absolutely cannot craft it.
I did had Daedric at one point but I like Dawnguard armor more personally so I prefer wearing Dawnguard armor now on my main. On all my other chars, they wear what suits them.
I've never intentionally tested it, so I can't say with certainty, but I have noticed that if I loot a chest and I die shortly afterwards, re-load my save and loot that same chest, it always contains the same contents. So I'm not saying contents don't change with re-attempts, but in my brief experience, that's not the case.
No. When the loot in a chest is loaded, it stays like that even if you reload a save.
There are only two ways of changing the loot... One is wait the right amount of days for it to change on its own or leave the area then exit the game totally and reload the whole game, this'll reset the loot. Will also reset shopkeepers and everything else.
As in... Exit the game and go back to Xbox Dashboard/PS3 Dashboard/etc then hit "Play Skyrim" to load it back up again then load your save and boom, reset.
Everything time when I load Skyrim and my main save, first thing I do is go straight and get about 400 steel bolts at Dawnguard Castle. Gotta keep my ammo up after all!